import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 19182
 * Date: 2025-10-23
 * Time: 21:00
 */
public class UdpEchoServer {
    DatagramSocket socket = null;
    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动");
        while(true){
            //构造请求数据包接受请求
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());
            String response = process(request);
            //记得加上客户端的IP和端口号，才能找到客户端和上面的进程
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),response.getBytes().length, requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("[%s:%d] req:%s, res:%s\n", requestPacket.getAddress().toString(), requestPacket.getPort(), request, response);
        }
    }
    private String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer = new UdpEchoServer(9090);
        udpEchoServer.start();
    }
}
